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Old 16th Mar 2019, 10:24 pm   #18
cathoderay57
Nonode
 
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,364
Default Re: Marconiphone 855 Silent on 49m

Hi Lawrence. In post 13 the Marconi 855 was, I'm certain, not oscillating and was therefore receiving nothing anywhere on the 49m band, and so it did not pick up any signals from the DR49 oscillator. I had already done a systematic test anyway with my signal generator injecting tone modulated signals at 41m and then slowly decreasing the Sig gen frequency and following the signal on the 855 by adjusting the tuning knob. As it approached 49m everything went silent. That was done with an X63 frequency changer fitted whereas in post 15, I had a 6K8G fitted. I think that was fair game as merely swapping the 2 valves could not have shifted the alignmen by 2x465kHz. I do have a basic scope but no RF probes so I have never had any success connecting it to old radio oscillator circuits as the act of connecting the scope leads (presumably capacitive effects) prevents a meaningful measurement. Cheers, Jerry
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